In much of the agricultural industry, because weed control is now primarily done using herbicides rather than tillage, tillage of the soil has become greatly reduced, and it is currently very common to conduct “no-till” agricultural operations with no tillage at all. The furrow openers on modern seeding implements cut narrow furrows in the soil surface and agricultural products such as seed, fertilizer, and chemicals are deposited in the furrows. In an air seeder the furrow openers are evenly spaced across the width of an implement frame and the products are conveyed by a pneumatic conveyor system from product tanks to the furrows made by the furrow openers as a tractor tows the air seeder along the field.
The product tanks can either be mounted on the implement frame or on a separate tank cart towed either behind the implement frame or forward of the implement frame. While it is known to mount narrower width implement frames directly to a tractor or to a tank cart, more typically the implement frame is mounted on wheels and connected to a towing vehicle by a drawpin such that the towing vehicle and implement frame pivot with respect to each other about a vertical pivot axis. Where the air seeder includes a tank cart towed forward of the implement frame, known as a “tow between cart”, the tank cart is connected at the front end thereof to the tractor by a drawpin and the implement frame is connected to the rear end of the tank cart by another drawpin. Where the air seeder includes a tank cart towed behind the implement frame, the implement frame is connected at the front end thereof to the tractor by a drawpin and the tank cart is connected to the rear end of the implement frame by another drawpin. The tow between cart severely reduces the visibility of the furrow openers and the ability of the operator to detect and correct plugging and like operational problems, and so the tow behind cart has become more popular.
As modern farms grow in size, air seeder manufacturers make wider air seeders with larger product tanks to cover more field area per hour and reduce the necessity to stop and refill the product tanks Thus present day air seeders can be very wide, up to 90 feet or more, and the product tanks can carry 1000 bushels or more of agricultural products, and the tank carts thus weigh 100,000 pounds or more when full, and even empty these carts weigh 30,000 to 40,000 pounds.
Tractors used to pull such large air seeders typically have 500 to 600 or more horsepower (HP). Tractors are generally ballasted to weigh about 100 pounds per horsepower to have sufficient traction to transfer the horsepower to the ground, and these large tractors thus weigh 50,000 to 60,000 pounds. Thus, a large air seeder train can weigh over 150,000 pounds, and this weight passing over the field surface can cause soil compaction, especially in some soil types, and reduce productivity in the soil over which the wheels of the train pass.
HORSCH Maschinen GmbH of Sitzenhof, Germany manufactures a self-propelled air seeder with an operator's station at a front end of a vehicle and a plurality of product tanks mounted on the same vehicle behind the operator's station, essentially combining the tractor and product tank cart of the conventional air seeder and reducing the weight. A furrow opener implement comprising an implement frame supported on wheels is connected to the rear end of the vehicle, and product is carried from the product tanks to the furrow openers by an air stream. Like the tow between cart, the large tanks directly behind the operator's station block virtually any view of the furrow openers, except those on the extreme right and left outer ends of the implement frame.
Lemken Co. of Alpen Germany have manufactured a similar self-propelled air seeder with a mounted implement frame carrying furrow openers and ground working tools. Because the furrow opener implement is mounted directly to the propulsion vehicle, the width of this machine is limited compared to the 80-90 foot wide implements desired in modern farming on large acreages.
External guidance systems include receivers mounted on the vehicle to receive location information from global positioning systems (GPS), ground based signal towers, lasers, and the like and are now commonly used to automatically steer tractors pulling air seeders and like agricultural implements to follow a desired path. After the boundaries of a field have been defined by a headland pass, the guidance system will keep track of where the seeding implement is located and provide guidance to accurately cover the field, one swath or pass at a time until the field has been fully covered. At the outset, tractors and self-propelled equipment such as field sprayers equipped with these “auto-steer” systems required human intervention to control starting and stopping the application of the agricultural products at the correct time, and to make the headland turns. The newest auto-steer systems can now control the application of agricultural products and make the headland turns without human intervention. Also, when irregular shaped areas within a field are encountered, GPS based systems have now been developed to identify overlap areas and prevent double application of the farm materials.
Such modern guidance systems can determine the location of the furrow openers to within two inches or less, and the aim is to guide the furrow openers in each pass so that a consistent spacing, typically about 10-12 inches, is achieved between the end furrow opener on one implement pass and the end furrow opener on the next adjacent pass.
Location sensors can be used to accurately determine the location of the furrow openers on the implement frame however since guidance is provided by the tractor at the front end of the train, significant deviations can occur, especially where a series of vertical pivotal connections is present between the furrow opener implement and the tractor. A heavy product cart at the rear of the chain of implements can also pull the furrow opener implement off course on sloping terrain.
In air seeders where all the product tanks are mounted on the implement frame, there is no tank cart and so there is only a single vertical pivot axis and the guidance is more accurate. With the larger product tanks desired for wide air seeders however, it is not practical to mount all product tanks on the implement frame, so larger air seeders typically require a tank cart.
The growing sophistication of external guidance systems has also led to the development of unmanned tractors, such as manufactured by Autonomous Tractor Corporation of Fargo, N.D. These tractors have diesel-electric drive and are guided by a laser based external guidance system, and include a remote control that allows control by a remote operator. A large fuel tank allows for 36 hours of operation, and a ballast tank allows the weight of the tractor to be increased or decreased as conditions might warrant by adding or removing water.
Conventionally, farmers would typically own a number of tractors of different sizes to pull the varied implements used in their operations. A large high powered tractor was used to pull the widest heavy implements that were used for tillage and seeding, and often as well to power large combines at harvest time. Smaller tractors might be used for spraying, to operate a loader, or for mowing and like lighter jobs.
Since the advent of no-till seeding, tillage is no longer carried out by many farmers. Combines of the type that are pulled behind large tractors are also no longer much in use. The result is that on many farms the largest tractor is used only for pulling the air seeder at seeding time, and sits idle for the rest of the year.